How to trim a video.

So you took a video but really only 5 seconds is interesting.  You can easily cut off the beginning or end or both in the photos window.

Click on photos
Select Camera roll
Play the video

Now here is how you trim...
At the top of the page is a bar showing the length of you video.

Very carefully touch the beginning of the video, the band around the video will turn Yellow.  Then move the starting point to where you want your video to start.

Do the same for the end of the video by selecting the right side of the band.

If you make a mistake you can either keep moving the yellow band or click cancel at the top left corner.

Once you have your video to the length that you want just click trim at the top right corner.